A study of the occurrence of peptide nitrogen in the blood.

Abstract

The nitrogen found in tungstic acid blood filtrates, which cannot be attributed definitely to any known nitrogenous substances, has been studied by the following method: To 10 cc. of tungstic acid blood filtrate in a large test-tube graduated to 25 cc. are added 10 cc. of a saturated solution (room temperature) of barium hydroxide. The test-tube is fitted with a reflux condenser, and the contents kept boiling gently for 20 to 24 hours. The solution is then concentrated to 5 cc., a drop of 0.25 percent phenolphthalein is added and sufficient 2 percent sulfuric acid to precipitate the barium. Water is added to the 25 cc. mark, and the contents shaken and filtered. The determination of the free and hydrolyzed amino acids is carried out according to the method of Folin.1 The difference between the free and total amino-acid nitrogen is considered as peptide nitrogen.In a recent paper Blau2 came to the conclusion that the amount of peptide nitrogen is by far too small to account for the undetermined nitrogen. T...